Planting apple trees
Great choice, Roxbury Russets are really delicious apples (and I don't just say that because I grew up & live near Boston!).
I actually work for an organization that plants heirloom apple trees, and one of the most important things to keep in mind is that apples need another tree within at least a quarter / half mile (preferably closer) of a different variety in order to set fruit when it gets to that point. So if there are no other apple trees (including crab-apples) in or around your parents' yard, I would suggest getting another tree (not another Roxbury Russet) and planting it nearby.
We have a list of instructions on our website that includes a video on planting apple trees: http://www.bostontreeparty.org/resources/planting-instructions/. Elsewhere on our site we also have a list of other heirloom apple varieties that are great: http://www.bostontreeparty.org/resour....
Lots of community groups do apple pruning workshops, and pruning can get pretty complicated especially as trees age, so if there are any of those offered near your parents I would really recommend they consider attending an in-person workshop – it really helps to see an expert do it in person before you tackle your own trees!